Cycas

Sago Cycad and Their Relatives

Trees of the genus Cycas are primitive gymnosperms that superficially resemble palm trees. However, they are quite distinct from true palms, and form an entirely different lineage.

Description and Identification

Cycas trees – like most other members of the class Cycadopsida – feature a ring of pinnately compound (feather-like) leaves attached to the top of the trunk. You can further recognize members of the genus by noting the prominent mid-ribs of the leaflets and lack of any obvious secondary veins.

Like all other cycads, trees of the genus Cycas are dioecious, with distinct male and female plants. In both cases, the cones lie at the top of the trunk and emerge from the center of the leaf ring.

While some members of the genus feature round, subterranean trunks and are essentially shrub-like, others have tapering, tree-like trunks that grow aboveground. Most cycads feature relatively shallow root systems and grow very slowly. The majority of species remain rather small, with the largest specimens reaching perhaps 35 to 40 feet in height.

Relatives and Relationships

Between 90 and 115 species comprise the genus Cycas (the only genus in the family Cycadaceae), making it one of the largest lineages in the class Cycadopsida. Commonly known as the cycads, the ancestor of this group of species is thought to be the sister lineage to the other families in the class.

Cycads are ancient species that were found across most of the world by the beginning of the Triassic period. In fact, the entire Mesozoic era (which spanned from approximately 225 million years ago to 65 million years ago), is often called the “Age of the Cycads,” because of the plants’ dominance in these ecosystems. According to the University of California, Museum of Paleontology, cycads represented one-fifth of the world’s flora during much of the Triassic and Jurassic periods.

Habitats and Geography

Cycas trees are confined to the Old World. They are found from Japan, west to Africa and Madagascar, and south as far as northern Australia. As a group, the trees inhabit a variety of landscapes; some forms grow in tropical rainforests, while others grow along rocky escarpments.

Some species, for example, Cycas circinalis are well adapted to living along shorelines. The seeds of these trees are buoyant and capable of lasting extended periods of time floating through the ocean, until they eventually wash up in a habitable location.

Culture and Uses

One of the most commonly cultivated species is the so-called sago palm (Cycas revoluta). It prefers full sun, but some people succeed in growing them indoors. Because they remain relatively small, they are often planted in restricted spaces. If provided with a suitably large vessel, sago palms often thrive when grown in a container.

Several indigenous cultures throughout the range of these plants collect and eat the trees’ seeds as a food source, and some harvest starch – called sago — from the stems. However, neurotoxins are found throughout many different portions of the plants; if consumed, the poisons can cause serious disease or death. Accordingly, most people who eat the seeds or sago attempt to leach out the toxins with copious amounts of water.

Encephalartos_altensteinii,_Waterberg

African Cycads

Appearing somewhat like palms or ferns, African cycads are primitive trees, native to the southern half of Africa.  As part of the family Zamiaceae, African cycads display many similarities to their relatives in other genera.

Description

Like other cycads, African varieties produce a circular ring of compound leaves at the top of their trunks. Most species have distinct trunks, although other species grow as multi-trunked “shrubs.” Some species, such as Encephalartos hirsutus, produce ground-hugging stems. Suckers commonly emerge from the base of the trunk in many species.

Like other cycads, these are dioecious trees, which produce either male or female cones. Many people find the odor associated with the male cones to be rather off-putting. The seeds of these gymnosperms are often brightly colored, which probably helps them to attract predators, who may spread the seeds in their droppings.

Like the other cycads, African cycads are usually rather small. However, Encephalartos laurentianus – the largest species in the genus – occasionally exceeds 45 feet in height. Another species, Encephalartos transvenosus reaches similar heights, and may reach 40 feet in height.

Species

The genus Encephalartos contains approximately 60 to 65 species; the exact figure varies depending on the authority consulted. The majority of the species are sun-loving plants that require well-drained substrates. Some consider these cycads to be succulents, as they store water in their trunks.

Some African cycads are very poorly understood by botanists, and they appear to be quite rare in the wild. Many are listed as “Endangered” or “Critically Endangered” by the IUCN Redlist of Threatened Species. For example, only a single male specimen of E. woodii is known to exist in the wild. The specimen, which was first documented in 1895, grows in the Ngoye Forest, in Zululand. Several other specimens – all derived from cuttings taken from the original wild plant – grow in a handful or arboreta and botanical gardens.

Others have only been found in a very restricted range. For example, the vast majority of E. aemulans live on a single hill in the Natal region of South Africa. It is possible that the species’ former range was more extensive, as two aged male specimens are located about 5 miles away from the hill. This species was only formally described in 1993, and prior to this, many specimens found their way into the ornamental plant market. Currently, the wild population is protected, and, according to the Gymnosperm Database, the location has not been made publicly available.

By contrast, other species of the genus are thought to have relatively healthy, stable populations. Some species are imperiled in one part of their range, yet safe in other locations. For example, most Kenyan giant cycads (E. tegulaneus) populations are stable, but some are critically endangered.

Common Uses

Like many close relatives – including sago cycads (Cycas revoluta), among others – African cycads harbor edible starches in their trunks. This material usually undergoes quite a bit of processing before it is consumed, as the material contains poisons. Nevertheless, several members of the genus are colloquially called “bread trees” in their native range. The hollow trunks of some African cycads are used as water dishes for livestock.

Several African cycads are popular ornamental plants. E. altensteinii and E. ferox are two of the most widely available species, but E. arenarius, E. cerinus and E. kisambo are relatively common as well.

Various primates, rodents, birds and other wildlife species consume the fruits, as do some humans from the region. The outer portions of the kernel are regarded as edible, while the internal kernel is quite toxic; however, many authorities recommend against eating the seeds entirely.

Outeniqua_Yellowwood

African Podocarps

The so-called “African podocarps” include six species of tree within the genus Afrocarpus. They exhibit numerous similarities with the more familiar and widespread Australasian podocarps (Podocarpus spp.), and they were formerly classified in the same genus. Several different colloquial names are applied to members of the genus, including yellowwood, yew and fern pine.

Species

Two members of the genus are relatively well known: the Common Yellowwood (Afrocarpus falcatus) and the East African Yellowwood (Afrocarpus gracilior). Both reach respectable size, with gracilior reaching up to 120 feet in height and falcatus occasionally reaching 140. However, common yellowwoods usually only attain such heights when they grow in ideal locations.

By contrast, many other members of the genus are relatively poorly known. For example, some workers believe that the Madagascan endemic Afrocarpus gaussenii represents a distinct species, while others suggest that it is a variety of the common yellowwood.

Distribution

Podocarps are largely trees of the highlands, and they are primarily found in two north-south bands, with one occurring on the eastern half of the continent and the other occurring on the western half. However, a small population of common yellowwoods grows throughout lowland habitats in South Africa and Mozambique.

Nevertheless, some confusion surrounds the range of some African podocarps. For example, many authorities state that the podo (Podocarpus usambarensis) is only found in Tanzania, while others believe it occurs in Kenya, Burundi, Rwanda and Uganda as well.

Unlike many other conifers, African podocarps rarely form pure stands; instead, they often spring up as individual forest trees.

Characteristics

African podocarps resemble their Australasian counterparts in most respects. Like their relatives, they possess elongated evergreen leaves, with either a distinct midrib or parallel veins. Some specimens exhibit a shrub-like growth habit, but most forms grow as proper trees. Large specimens may exceed 120 feet in height, although most are much smaller.

Like their Australasian counterparts, many African podocarps produce fleshy, fruit-like cones with a bulbous, colorful aril. The bright colors help attract birds and arboreal mammals, who consume the cones and expel the seeds in their droppings. Interestingly, the fleshy covering of yellowwood seeds is thought to inhibit germination, as the seeds usually fail to sprout unless the majority of the fleshy material is removed, as occurs in the digestive tracts of animals.

African podocarps are moderately long-lived trees, although much remains to be learned about their lifespan. At least one specimen was confirmed to have lived for over 700 years.

Commercial Uses

African podocarps are important timber trees in many parts of Africa, thanks to their high-quality, fine-grained, yellow wood (from which they derive their common name, yellowwood). For example, lumber from common yellowwoods is used in the construction of furniture, window frames and in ship construction. However, the overharvest and illegal logging of some species has led to population declines in many areas; according to the IUCN Redlist, as much as 50 percent of the historic population has disappeared since the 1950s. South Africa and a few other African nations now protect these trees, and prohibit their harvest.

Yellowwood bark is used in commercial tanning facilities, and many locals consume the fruit. Yellowwoods also serve important roles in the lives of many animals. Bats, birds, pigs and monkeys consume the fleshy seeds, and arboreal critters, including Chacma baboons (Papio hamadryas); use the trees’ dense crowns as shelter.

Pseudotsuga_menziesii_Tiger_Mountain_Seattle

Douglas-Firs

Approximately six species comprise the genus Pseudotsuga, colloquially known as the Douglas-firs. They are some of the most iconic trees of the Pacific Northwest, and they often grow as pure or nearly pure stands. The trees are very important commercially, which has caused them to become interwoven with local cultures. For example, Douglas-firs are Oregon’s official state trees.

Basic Description

Douglas-firs are large, evergreen trees that are an early successional species. They grow very quickly when bathed in direct sunlight, such as occurs in areas cleared by fire or along the edges of established forests, but they languish in the dim light below established canopies.

As young trees, Douglas-firs have smooth, gray bark, but as they age, the bark becomes thicker and fissured. Like other conifers, they lack true flowers; instead, they produce, store and release pollen from small, red-yellow cones. Their seed cones, which broadly resemble pinecones, grow on 2-year-old twigs, and feature long, feathery bracts. Douglas-fir seeds represent a very important food source for most small herbivores and omnivores that share their range, including a variety of songbirds, squirrels and mice.

Classification and Diversity

Although the term “Douglas-fir” may refer to the entire Pseudotsuga genus, most people use this term to refer to a single species – Pseudotsuga menziesii. This species has a scattered distribution pattern, ranging across much of the western United States, as well as portions of Canada and Mexico. Most botanists recognize two or three varieties (or subspecies) of this species.

Coastal Douglas-firs (Pseudotsuga menziesii var. menziesii) grow along the western boundary of the species’ range, while Rocky Mountain Douglas-firs (Pseudotsuga menziesii var. glauca) grow, as their name implies, farther inland. Some researchers consider specimens growing in Mexico to represent an additional variety (Pseudotsuga menziesii var. lindleyana), while others consider these trees as part of the Rocky Mountain variety. The only other U.S. species is the bigcone Douglas-fir (Pseudotsuga macrocarpa), which grows throughout southern California.

Few of the other members of the genus are commercially important, and most of them inhabit rather restricted ranges in Asia. At least three species in the genus – Pseudotsuga sinensis, Pseudotsuga japonica and Pseudotsuga brevifolia – are classified as “Vulnerable” in their native ranges.

Size and Age

Douglas-firs often become massive trees. A few of the largest living specimens reach more than 300 feet, but historical accounts detail a few trees approaching 400 feet in height. Currently, a specimen known as the Brummit Fir stands approximately 325 feet high, thereby making it the tallest living Douglas-fir, the tallest living member of the family Pinaceae and the third tallest living tree in the world. Some of the oldest and largest specimens have massive trunks of up to 20 feet in diameter.

Although they are fast-growing trees, it takes the tallest specimens a very long time to reach such heights. Most of the tallest examples are found amid the few remaining old-growth forests. Many live for 600 or more years, and several have been alive for the last 800 years. The maximum documented age is 1350 years, but this age was determined from a stump, not a living tree. Thanks to their long life spans and tendency to produce regular growth rings, Douglas-firs are often used to study climate change and the impact of air pollution on tree growth.

Commercial Uses

Douglas-firs are some of the most important timber trees in the world, and they have been harvested extensively over the last 200 years. They are used in a variety of construction contexts, and are made into everything from dimensional lumber to plywood.

Douglas-firs are commonly used as landscape trees, particularly in screening projects. The trees are also commonly grown as Christmas trees.

Podocarpus

Australasian Podocarps

Podocarpus is a genus of trees and shrubs, primarily restricted to the southern hemisphere. Most of the 100 or so species in the genus are dioecious (meaning that individuals produce either male or female reproductive structures – not both) and possess elongated leaves, varying from about 1/2 to 6 inches in length, with a distinct midrib.

Members of this genus are close relatives of the African genus Afrocarpus, which is also part of the family Podocarpaceae. The two to six recognized members of Afrocarpus were formerly classified in the genus Podocarpus and some texts still refer to these African species as such.

Modest Sizes

Most podocarpus grow as small trees or large shrubs, but the genus does exhibit some diversity. For example, like many species within the group, broadleaf podocarps (Podocarpus nagi) reach little more than 25 feet in height, while the tōtara (Podocarpus totara) occasionally exceeds 100 feet in height. Horticulturists have also created a number of cultivars that exhibit unusual growth forms or habits.

Fantastic Fruit

Like other conifers, podocarps are cone-producing plants. However, their cones do not resemble the familiar cones of pines, spruces and firs; instead, they are more reminiscent of the fleshy cones produced by junipers (Juniperus spp.). Most podocarp fruits consist of a dark-colored seed, with a fleshy red, orange or purple structure attached to the proximal side, called an aril.

Many bird species feed on the flamboyant fruits and spread the seeds in their droppings. While humans sometimes consume the fruit, many authorities caution against the practice, explaining that the seeds – and to a lesser extent, the arils — are toxic.

Male plants producing drooping cones, which produce and release pollen. Like other conifers, podocarps lack showy flowers, and are therefore wind-pollinated.

Commercial Uses and Applications

The interesting appearance of podocarps cause many landscapers, homeowners and gardeners to use them as ornamental trees. Some plant them as specimen or accent trees, while others plant them as hedges or screens. Most podocarps require well-drained, slightly acidic soil to thrive; alkaline soils can cause the foliage to turn yellow.

One particularly popular species is the Buddhist pine (Podocarpus macrophyllus), which usually grows as a large shrub or small tree. Native to southern Japan and China, Buddhist pines are often used by bonsai enthusiasts.

Allergens

Male podocarps produce an abundance of highly allergenic pollen; the OPALS allergy scale rates them a 10 (the highest score). By contrast, females produce no pollen of their own, and they actually absorb some of the pollen produced by males, which earns them an OPALS rating of 1 (the lowest possible score). Accordingly, those seeking to add podocarps to their landscape should opt for female plants whenever possible.

Urban Ambassadors

Many podocarps adapt well to urban environments. They are especially useful for locations with restricted soil areas, as the roots rarely cause damage to nearby sidewalks and hardscapes. Additionally, many podocarps are quite drought resistant and require little to no supplemental irrigation.

The branches of some podocarps droop toward the ground, where they may block visibility or access. However, this is readily rectified by removing the lower limbs on the trunk (a technique called crown raising).

Tsuga-diversifolia

Hemlocks

The eight or so described hemlock species (Tsuga spp.) are evergreen trees who reproduce through cones, like all other living conifers. However, because of their preferred habitats – cool, rainy areas — hemlocks exhibit a variety of traits and tendencies that are at odds with most other conifers.

Description

Hemlocks produce branches that are often arranged as flat, drooping splays. The needle-like leaves attach singly to the branches. Some Tsuga species bear needles in a single plain, while others bear needles that point in virtually every direction. The brown bark of hemlocks is usually scaly or flaking, and often becomes deeply fissured on mature specimens. Hemlock pollen cones are brown and rather unremarkable; seed cones are rather small, but they are quite attractive.

Hemlocks are medium-sized conifers, commonly reaching 40 to 80 feet in height. However, some of the tallest specimens (located in the western United States) reach 180 feet in height. Although they are generally considered climax species, hemlocks rapidly colonize disturbed areas, thanks to their ability to grow very quickly when provided with abundant sunlight. In most places where they occur, hemlocks eventually dominate the habitat.

Range and Diversity

Hemlocks grow in several portions of North America and Asia. Carolina hemlocks (Tsuga caroliniana) grow in the southeastern United States; eastern hemlocks (Tsuga canadensis) replace them to the north, living throughout the eastern U.S. as far west as Minnesota and north into eastern Canada. Western hemlocks (Tsuga heterophylla) are found living along the western coast of the continent, from Alaska to California. Mountain hemlocks (Tsuga mertensiana) also grow along the west coast and their range overlaps that of the western species; however, the mountain hemlock primarily occurs at higher elevations than its sympatric conspecific.

Taiwan hemlocks (Tsuga chinensis), northern Japanese hemlocks (Tsuga diversifolia), southern Japanese hemlocks (Tsuga sieboldii) and Himalayan hemlocks (Tsuga dumosa) all hail from their namesake regions. Forrest’s hemlocks (Tsugaforrestii) range throughout portions of China.

Hemlock Wooly Adelgid

In the early 1950s, a small insect native to Japan was found feeding on hemlocks in Virginia. The insect– known as the hemlock wooly adelgid (Adelges tsugae) — is a member of the order Hemiptera (the “true bugs”). Like other true bugs, these adelgids have piercing-sucking mouthparts, which they use to feed on the sap of the hemlock trees.

Inflected trees usually fade from the deep emerald green color characteristic of healthy specimens, to a pale, grey-green color. Most affected eastern hemlocks eventually die from the infestation. According to some estimates, half of the population of eastern hemlocks has been affected by the invasive adelgid. In their native Japan, the insects do not often cause serious problems, because their population is kept in check by a predatory beetle, Sasajiscymnus tsugae. This beetle is currently being used in the eastern United States to help combat the adelgid.

Ecologists fear that the loss of hemlocks will lead to problems in other species, as the trees play several crucial roles in their native habitats. For example, hemlocks often grow alongside streams, where their foliage helps to shade the water, thereby keeping the water temperatures low enough for native trout species. While a native species of hemlock wooly adelgid lives in the Pacific Northwest, western hemlocks rarely die from attacks by these insects.

Commercial Uses

Hemlock wood is moderately strong, and it has become more commonly harvested for timber purposes over the last several decades. Hemlocks make very attractive and hardy landscape trees, but it is important to avoid planting them in drought-stricken regions unless you can provide supplemental irrigation – hemlocks are much less drought tolerant than most other conifers.

Because they are very tolerant of shade, they often thrive in areas where few other conifers will. Several cultivars of the eastern hemlock are available commercially, giving landscapers even more options for incorporating these beautiful trees.

Picea rubens

Spruces

About 35 species make up the genus Picea – the spruces. Like other members of the family Pinaceae, they are evergreen conifers, related to the hemlocks (Tsuga spp.), firs (Abies spp.) and Douglas firs (Pseudotsuga spp.); however, their closest relatives are the pines (Pinus spp.). Botanists generally agree that the group originated in western North America (the earliest fossilized material from the group was found in Montana), but they currently grow throughout portions of Asia and Europe as well.

Challenging Identifications

Determining that a given tree belongs to the genus Picea is relatively easy. Most spruces have short, sharp, stiff needles that are rarely longer than 1 inch. Each needle attaches singly to the branch via a small, peg-like structure called a pulvinus. These pulvini provide one of the most obvious clues to identify the trees as spruces: They cause the branches of mature trees to feel bumpy.

Spruces typically have scaly bark, and pendulous cones, rather than the upright cones that typify true firs. Additionally, their cones are usually covered in paper-thin scales, rather than the thick scales characteristic of pines and some other conifers. However, like the cones of pines, the base of each scale bears two seeds (although not all scales have seeds – those near the top and bottom of the cone are often sterile).

However, while it is relatively easy to identify a tree as a spruce, it is often challenging to identify the tree to species level. Location provides perhaps the best clues, but it is usually necessary to examine the details of the cones and flowers to identify specimens to species level.

Description and Distribution

Spruces have a conical growth habit, although several cultivars are available that may display a number of different forms, including ground hugging, globular and weeping. Some spruces reach very impressive sizes – a few reach 200 feet in height, but most are between 60 and 120 feet tall.

Spruces are limited to regions with cool climates. Some forms grow in subtropical mountain ranges, but the bulk of the species are at home in the boreal forests of the Northern Hemisphere. In fact, spruces are the dominant forest species throughout much of Asia, Scandinavia and Canada.

Aging Gracefully

Like many other conifers, most spruces have long lifespans; many species are capable of living for at least 800 years. However, some are much older than this — scientists currently consider a 10,000-year-old spruce living in Sweden to be the oldest living tree. However, this particular tree is a clone that sprouted from the original tree in a process called layering; therefore, while the wood of this current tree is not 10,000 years old, the tree (in its various iterations) has lived for this entire time period.

Because of the harsh climate of the location, this particular spruce lived as a shrub for the last several decades or centuries. However, rising global temperatures have recently allowed it to begin taking on a single-trunked, tree-like form.

Commercial Uses

While they may not be quite as commercially important as the pines are, spruces do provide humans with several important resources. One of the most important uses of spruce wood is the manufacturer of paper, as the long fibers of the wood make for exceptionally strong, high-quality paper. The wood is also used in construction, but because it has poor resistance to insects and decay, it is primarily used for interior applications. Spruce wood is also prized for the construction of some musical instruments, especially guitars, violins and other stringed instruments.

Spruce trees also function well as ornamental trees, and a few species are popularly used as Christmas trees. Most firs appreciate cool temperatures, protection from the wind and full sun to partial shade. A few cultivars are known for being drought-resistant, although most require regular irrigation in well-drained soils.

Pinus longaeva

Pines

Clad in evergreen needles and decorated with handsome woody cones, pine trees (Pinus spp.) are among the most recognizable trees in the world. In addition to their aesthetic charm, pine trees provide a variety of resources to the ecosystems in which they grow. This not only includes the sustenance and shelter prized by wildlife, but the raw materials humans have used to build everything from homes to fences to furniture.

Meet the Family

The term “pine tree” applies to all members of the genus Pinus. Different authorities recognize different levels of diversity within the genus, although most works report between 130 and 170 living species. Within the genus, pines exhibit considerable variation in life history and physical traits.

For example, Siberian dwarf pines (Pinus pumila) — one of the smallest species in the genus – are essentially shrubs that rarely exceed 10 feet in height. Conversely, ponderosa pines (Pinus ponderosa) are one of the largest members of the genus, and they may exceed 200 feet in height; the tallest documented specimen is approximately 270 feet high.

The living pines are grouped into several subgenera, each of which contains a collection of closely related species. The subgenus Pinus includes a number of two- or three-needled species with hard, yellow wood, while the subgenus Ducampopinus is comprised solely of the pinyon pines. The white pines (subgenus Strobus) have soft wood and needles bundled in groups of five.

Bundled Needles and Seed-Bearing Cones

Most pines are instantly recognizable by noting their bundled needles (the bundles are often called fascicles), which bear a deciduous sheath around the base. Most species produce needles in bundles of two to five, although there are exceptions, such as the single-leaved pinyon pine (Pinus monophylla), which produces single needles. The leaves are evergreen and vary in size from one species to the next. For example, whitebark pine needles (Pinus albicaulis) may measure slightly more than 1 inch, while longleaf pines (Pinus palustris) of the southeastern coastal plain may produce needles measuring up to 18-inches in length.

While they are similar to those of many other conifers, pinecones are also iconic characteristics of pines. Comprised of numerous rows of woody scales, pinecones remain tightly closed when they are young. When they open, the seeds are released to the forest floor below. A few varieties retain their seeds until birds separate the scales and remove the seeds manually. The seeds then pass through the digestive tracts of the birds, and germinate where they are deposited.

Other pine species rely on fire to help disperse their seeds, as the seeds remain inside serotinous (resinous) cones that remain tightly closed until the high temperatures of a forest fire melt the resin and allow the cones to open. At this point, the seeds may fall onto the recently burned earth, where they will grow rapidly, courtesy of the abundant sunshine and lack of competitors.

Ecology and Adaptability

Although Sumatran pines (Pinus merkusii) slightly encroach into the Southern Hemisphere, pines are largely restricted to the Northern Hemisphere. Nevertheless, pines inhabit a variety of habits throughout much of North America, Europe and Asia. As a group, pines exhibit a number of adaptations to these varied habitats that allow them to survive.

For example, while most pines prefer well-drained soils, lodgepole pines (Pinus contorta) grow readily in damp earth. Whereas Great Basin bristlecone pines (Pinus longaeva) are exposed to high winds, which lead them to grow in twisted, contorted manners, forest-grown sugar pines (Pinus lambertiana) grow tall and straight. .

Commercial Importance

Pine trees are some of the most commercially important trees in the world. Early European settlers, for example, harvested broad swaths of white pine (Pinus strobus) growing throughout east-coast forests to make their houses and other items. In addition to their considerable timber value, the seeds of many pines are edible and delicious – especially those from Korean pines (Pinus koraiensis), which are intensively managed in China.

Pines also make excellent ornamental trees, and because they live in a wide range of habitats and geographic regions, most property owners can find a species suitable for the site. This is especially true of California-based property owners, as 19 species are native to the state and many others are suitable for the region’s climate and geology.

True Cedars

True Cedars

Native to the Mediterranean region of Europe and the western portions of the Himalayan Mountains, cedars are relatively large, evergreen trees. They are not only important ecologically and for their commercial uses, but many cedars hold special cultural significance in their natural range.

The Name Game

Many species, including representatives of the genera Juniperus and Thuja, are bestowed with common names featuring the term “cedar.” In fact, the term “cedar” is applied to so many different types of trees that many tree professionals, farmers and botanists refer to trees of the genus Cedrus as “true cedars.” This represents yet another example in which use of the scientific (or botanical) name can help alleviate confusion.

Classification and Taxonomy

Taxonomists differ on the exact classification of the group, but most recognize four different species within the genus Cedrus: Deodar cedars (Cedrus deodara), Lebanon cedars (Cedrus libani), Cyprus cedars (Cedrus brevifolia) and Atlas cedars (Cedrus atlantica). It appears, according to the Gymnosperm Database, that Deodar cedars are the sister clade to the other three species. This means that while all four species share a common ancestor, Cyprus, Lebanon and Atlas cedars share a common relative that is not part of the Deodar cedar lineage.

Description

Cedars typically exhibit a pyramidal growth habit, and bear blue-green to light green needles. Unlike many other conifers, such as firs (Abies spp.) or white pines (Pinus strobus), cedars do not produce branches in whorls. Some cedars exhibit irregular growth forms, which can give them great character and visual interest.

The seeds feature interesting structures called resin blisters, which contain unpalatable substances. Presumably, these serve as a deterrent to squirrels and other seed-eating rodents. Once the cones mature, they open and fall apart to help scatter the seeds.

While some of the cedars are rather cold hardy, the Atlas cedar of North Africa is susceptible to damage in cold winter climates. Likewise, the various species exhibit different growth rates. Atlas and Lebanon cedars typically put on less than one foot of growth per year, while Deodar cedars are fast growers that will quickly outgrow insufficient planting spaces.

Common Uses

Cedar trees often thrive along the west coast of North America, and they make wonderful ornamentals. Although they usually remain much smaller in residential settings (between 40 and 70 feet in height and 20 to 30 feet in horizontal spread), some cedars grow to heights of 120 feet or more, so it is important to avoid planting them in restricted spaces. The graceful form of most cedars makes them excellent specimen trees, placed in an area that highlights their form. Several cultivars are available, including some very attractive pendulous forms, with drooping or weeping branches.

Cedar wood is famous for repelling moths; a fact which has led many to use cedar wood to construct closets and wooden items used in conjunction with clothing or shoes. The oils inside the wood give it a pleasant aroma, but these volatiles have allelopathic and insecticidal properties. Accordingly, cedar chips are often used as a pet bedding, in hopes that the aroma will cover offensive pet odors. However, care must be used, as some animals – particularly small reptile, amphibian and insect pets – can become sick or die upon exposure to cedar shavings. Additionally, many cedars – particularly fast-growing species, such as Deodar cedars – are also farmed for timber production. Because the wood takes oils and stains well, it is often prized for its handsome appearance.

Siberian-larch

Larches

Larches are medium to large trees of the genus Larix. Scientists debate the finer points of the group’s interrelationships and classification, but most recognize about 10 to 15 species.

Range and Geography

Most larches live in North America, Europe and Asia, although they have been planted in many other locations as ornamental species. Often, these trees are referred to as tamaracks in North America.

Eastern larches (Larix laricina) thrive in moist, acidic soils, while Japanese (Larix kaempferi) and European larches (Larix decidua) thrive in slightly drier soils. Most specimens are best adapted to live at high elevations, and some commonly live at heights of over 7,000 feet.

Description and Characteristics

In many ways, larches are unusual conifers – especially as it relates to their needles. Unlike the spiky or hard leaves of most conifers, larch leaves are soft to the touch. Larches are also deciduous trees that shed their needles each autumn. Like the needles of some other deciduous conifers, such as bald cypresses (Taxodium distichum), larch needles change color before falling off the tree. However, unlike bald cypress needles, which turn reddish-brown before dropping, larch needles turn brilliant yellow in the early autumn.

Additionally, larches produce and bear needles differently than most other conifers. The needles on the current year’s wood emerge singly, whereas those on older wood occur in dense clusters. Stout woody pegs (spur branches) sit at the base of these needle clusters. Larches produce relatively small woody cones, which average about 1 to 2 inches in length.

Larches shed their lower branches as they grow. Mature specimens often feature branchless boles for half or more of their length. Combined with their propensity for producing relatively sparse foliage, their self-pruning nature means that a relatively high level of light penetrates their canopies. This leads to a proliferation of herbaceous and shrubby growth beneath them. The bark of larches is characteristically thin and flaky.

Ecology

Larches are not especially important food sources for wildlife, although upland game birds and songbirds consume their seeds opportunistically. Birds also make nests in their bushy boughs. Mammals rarely rely on larches for food, but rodents, beavers and other animals occasionally nibble the bark, twigs and buds of the trees.

Most larches need full sun exposure to survive (which is part of the reason they shed their lower, shaded branches). They are very susceptible to competition from other plants, and cannot survive under shaded canopies. Even grasses or other plants growing under their canopies can stress them. Accordingly, larches are early successional species, quickly invading old fields and lakes that have been filled in by silt over the years. Larches often grow as pure stands, but black spruces (Picea mariana) are their primary associate in mixed forests.

Larches typically fare poorly in warm climates, so their use as an ornamental species is primarily limited to northern latitudes. Despite the fact that they often inhabit marshy sites, larches cannot tolerate submerged roots and their shallow rooting habit makes them susceptible to windthrow. While larches often colonize areas following wildfires, their bark provides relatively poor protection from fire.

Commercial Use

Larch wood is heavy, strong and relatively resistant to both water and decay. This has led to its use in a variety of applications. One particularly noteworthy use for larch wood is in the production of yachts. However, larches are not very important commercial trees, and most of the harvested trees are converted into pulp.